Current nasal delivery systems can adequately treat topical diseases, but are not suited to the delivery of substances to the upper part of the nasal airway, and in particular for targeted delivery to the olfactory region and sinus ostia.
The Turbohaler® as developed by AstraZeneca AB, where adapted for nasal delivery has not been a success. A large fraction of particles is deposited in the anterior region of the nasal cavity. Furthermore, the nasal cavity becomes narrower during nasal inhalation, thus further reducing the deposition efficiency in the posterior regions of the nasal airway, in particular in narrow and congested noses. There is also a considerable risk of inhalation of small particles to the lungs, as demonstrated in previous studies.